Process of scouring cellulosic textiles using steam



Patented May 3, 1949 UNITED STATES OFFICE PROCESS OF SCOURING CELLULOSICTEXTILES USING STEAM tion of Virginia No Drawing. Application November2'7, 1945, Serial No. 631,222

3 Claims.

The present invention relates to the finishing of cellulosic textiles,for instance unfinished cotton textiles and the like, and moreparticularly to finishing operations wherein the textile is subjected toa steaming while impregnated with a treating solution and is thereafterwashed.

The invention is of particular utility in the treatment of unfinished,predominantly cellulosic textiles, such as greige cloth, for the removalof natural color bodies, adhering solid impurities, such as motes,natural waxes and pectins and sizings, principally of starchy material,added to the textile during prior processing, and to improve the coloror absorbency of the textile.

An especially useful application of the process is in the scouring ofsuch textile materials by subjecting the textile to a steaming whileimpregnated with a caustic soda solution.

It has heretofore been proposed to scour textile materials by subjectingthem to a steaming while impregnated with a caustic soda solution forthe purpose of removing impurities and improving absorbency. However,such operations have not met with commercial favor for the reason thatuniform absorbency has not been readily obtainable by this method ofscouring. In order to obtain uniform absorbency it has been necessary torepeat the steaming operation a number of times, and even so,satisfactory results have not been consistently obtained.

In such operations as previously proposed, the textile after passingfrom the steamer has been piled into boxes or the like and carried tothe washer, or else has otherwise been subjected to substantial coolingin passing from the steamer to the washing operation. The Washingoperation has usually been carried out in cold water after the textilehas cooled to substantially room temperature.

We have discovered that surprisingly improved results are obtained insuch operations if the temperature of the textile be not permitted tofall below about 140 F. during the period of its passage from thesteaming operation to the Washing operation. Normally the textile willleave the steaming operation at a temperature of about 200-212 F., andwe have found it particularly desirable to maintain the temperature ofthe textile at not lessthan about 160 to 180 F. during the intervalbetween the steaming and washing operations. It is further desirablethat the washing. operation be carried out with hot water.

While we do not propose to be bound to any theory as to the reason forthe improved results obtained in accordance with our present invention,it is our present belief that in such operations as previously carriedout, the pectins and like impurities which are solubilized by thecaustic steaming become resolidified in the textile prior to washing sothat they are not completely or uniformly removed by thewashingoperation and that the presence of such resolidified impurities has beenresponsible, in part at least, for the lack of uniform absorbency of thetextile. By maintaining the textile at a temperature above that at whichany substantial resolidification of these impurities is effected, thematerials solubilized by the steaming treatment are readily anduniformly washed from the fabric, particularly if water at an elevatedtemperature be used in the Washing operation.

In scouring the textile, for instance, in accordance with our presentinvention, the textile is impregnated as by padding with the causticsolution, preferably hot, excess caustic solution is then drained orsqueezed from the textile and the textile wet with the caustic solutionis subjected to steaming. For this purpose, steam at atmosphericpressure is generally used and the textile will pass from the steamingchamber at a temperature of about 205-212 F. and from thence is passedto the washing operation without permitting its temperature to fallbelow about F., preferably not below ISO-180 F.

Various means may be provided for maintaining the textile at the desiredtemperature while passing from the steamer to the washer. For instance,the washer may be placed close to the exit end of the steamer andconnected to the steamer by a conduit or other meansfor preventingexcessive heat loss by the textile in passin from the steamer to thewasher. Where the washer cannot conveniently be placed close to the exitof the steamer, it may be desirable to mildly heat such conduit toprevent excessive heat loss from the textile to the surroundingatmosphere. In place of such a conduit, other suitable means formaintaining the textile at the desired temperature may be employed.

By maintaining the textile at the indicated temperature during itspassage from the steaming operation to the washing operation, and byusing hot wash water, good uniform absorbency has been obtained by asingle steaming of the textile, so that an even dyeing of the textile isobtainable without repeating the scouring operation, particularly wherethe textile is to be dyed a dark color. Where the textile is to be dyeda pastel shade it may be desirable to subject the treated textile to ableachin operation prior to dyeing.

The invention has also been found applicable to bleaching operationswherein the textile impregnated with the bleaching solution is subjectedto a steaming and subsequently washed. For instance, particularlyadvantageous results have been obtained by utilizing the presentinvention in conjunction with a bleaching operation whereby the textileimpregnated with an aqueous solution of a chlorite is steamed. In suchoperations, improved results have been obtained by maintaining thetextile at a temperature within the range previously indicated, whilepassing from the steaming to the washing operation.

In normal operation in a finishing mill, it has been found that even atthe high velocity at which the textiles frequently pass from oneoperation to another, while exposed to the atmosphere, the normaltemperature drop due to atmospheric cooling and evaporation is veryconsiderable, even over distances of travel of only a few feet. Evenwhen the textile is passed through an enclosed conduit, it has beenfound desirable to heat said conduit, as by means of steam, to atemperature of not less than about 180 R, if the length of the conduitis greater than about feet, assuming a velocity of travel of about 100yards per minute.

Where the textile is carried from the steamer to the washing operationin boxes, it may be necessary to protect the textile from heat loss inpassing from the steamer to the boxes and from the boxes to the washer.Also closed boxes may be used.

Though exceptionally satisfactory results are obtained in accordancewith our invention when hot water is used in the washing operation,greatly improved absorbency and uniformity of absorbency are obtained,even though cold water be usedin the subsequent washing operation.

It will be understood that the utility of our present invention is notrestricted to any particular method of steaming. It is, for instance,applicable to operations wherein the steaming is carried out in ropeform or is carried out at full width, and the textile may be impregnatedwith the scouring solution, for instance by immersion, padding, sprayingor any other satisfactory procedure which insures reasonably thoroughwetting of the textile.

Neither is the utility of the present invention restricted to anoperation wherein some particu lar concentration of the reagent isemployed. The concentration of the caustic solution, for instance, maybe varied over a considerable range in accordance with the recognizedpractice.

In bleaching operations, for instance, where sodium chlorite is used asthe bleaching agent, the impregnating solution may be either acid oralkaline. In scouring solutions such as caustic solutions, it has beenfound particularly desirable to include a detergent in the impregnatingsolution, for instance a synthetic organic detergent such as sulfated orsulfonated organic compounds active in alkaline solution.

The invention, as previously noted, is applicable to finishingoperations wherein the textile is steamed while impregnated with anaqueous solution of sodium chlorite, either acid or alkaline, dependingupon the nature of the impurities to be removed, as more particularlydescribed in our co-pending application Serial No. 357,280, filedSeptember 18, 1940, now abandoned. A further particularly desirableapplication of our present invention is in the finishing of textilescontainall ing predyed threads, as more fully described in theco-pending application of the present applicants and another, Serial No.358,664, filed September 27, 1940, in accordance with which the textileis steamed while impregnated with an aqueous alkaline solutioncontaining a minor proportion of sodium silicate, the sodium silicateserving to prevent the running of the dye of the predyed threadsnormally encountered in the treatment of such textiles with strongalkaline solutions. In each of these processes the textile is normallysubjected to a washing operation prior to further treatment, andparticularly desirable results are obtained in accordance with ourpresent invention by preventing the cooling of the textile to atemperature :below about F. between the steaming and the washingoperation. In many instances subsequent treatment of the textileheretofore found essential to the obtaining of the desired results maybe completely avoided, or at least such subsequent treatment materiallyreduced in extent or severity.

The invention will be further illustrated by the following specificexamples of its application. It will be understood, however, that theinvention is applicable generally to textile treating operations inwhich the textile is subjected to a steaming while impregnated with atreating solution and is thereafter washed.

Example I A cotton greige broadcloth, following the customary singeing,acid treating and drying, is impregnated with an alkaline aqueoussolution made up, for instance, of gallons of water, 60 pounds of a 25%solution of caustic soda, 6.5 pounds of sodium chlorite, and 10 poundsof a synthetic detergent consisting essentially of sodium ocenolsulfate. This solution is preferably applied hot to the textile, say ata temperature of about 125 1".

After draining or squeezing the excess solution therefrom, the textileis passed into a steam chamber and subjected to contact with steam atatmospheric pressure for about one-half hour.

The cloth leaving the steam chamber at a temperature of about 200-212"F. is then passed through a conduit heated to about 180 F. directly tothe washing operation wherein the textile is subjected to the customarywashing, preferably with hot water.

The absorbency of the textile thus treated has consistently been foundto be superior and more uniform than a textile similarly treated exceptthat it was permitted to cool to a temperature below 140 F. in theinterim between the steaming and washing operations.

Example II A cotton greige cloth containing predyed threads which underordinary conditions would run when subjected to steaming whileimpregnated with strong alkalis, is impregnated with an aqueous solutionhaving a pH of about 11-115 and containing about 1 of sodium silicate,about 3% of trisodium phosphate, and about /2% of a synthetic organicdetergent of the type noted in Example I. After removing the excesssolution, the impregnated textile is subjected to a steaming for aperiod of about one-half hour at atmospheric pressure, and thereafter,while maintaining the temperature of the textile at about C., thetextile is passed directly to a conventional washing operation whereinit is washed preferably with hot water.

Textiles thus treated have consistently been found to have a, moreuniform absorbency, and to be superior with respect to size and moteremoval, as compared with the same material similarly treated exceptthat the temperature was permitted to drop to below 140 F. during theinterval between the steaming and washing op erations.

In operations such as just described, considerable latitude ispermissible with respect to the concentrations and proportions of therespective reagents without loss of the benefits derived from thepresent invention. For instance, in the type of operation described inExample II, the sodium silicate constituent may vary from about /z% upto about 840%, or even somewhat higher. The pH of the impregnatingsolution is pref erably within the range of about 9.5 to about 12, andmay be adjusted by the addition of an alkaline material such astrisodium phosphate, scdium carbonate or tetrasodium pyrophosphate.However, in the presence of the sodium silicate, stronger alkalis, suchas sodium hydroxide, may be used without causing running of the predyedthreads. Trisodium phosphate, for instance, in proportions within therange of about up to about 5% may with advantage be incorporated in theimpregnating solution. The proportions of the other reagents maylikewise be varied over a considerable range so as to effect the desiredpH of the solution. Impregnating solutions having pH values evensomewhat in excess of 12 may be used.

In straight caustic steaming, the process is carried on as justdescribed, except that the impregnating solution is an aqueous solutionof caustic soda which may with advantage, though not necessarily,contain a detergent. In such solutions the concentration of the causticsoda may correspond to those used in ordinary kier 1 boiling and mayvary within the range, say, from about 0.5% to about 6.0% by weight.

We claim:

1. In the process of scouring cellulosic textile materials wherein thetextile, while impregnated with an aqueous scouring liquor, is subjectedto the action of steam in a steaming zone and is thereafter removed fromthe steaming zone and transferred to a physically remote washing zone,the improvement which comprises maintaining the textile at a temperaturenot lower than about F. during the interval between the steamingoperation and the washing operation.

2. In the process of scouring cellulosic textile materials wherein thetextile, while impregnated with an aqueous caustic soda scouring liquor,is subjected to the action of steam in a steaming zone and is thereafterremoved from the steaming zone and transferred to a physically remotewashing zone, the improvement which comprises maintaining the textile ata temperature not below about 40 F. during the interval between thesteaming operation and the washing operation.

3. In the process of scouring cellulosic textile materials wherein thetextile, while impregnated with an aqueous caustic soda scouring liquor,is subjected to the action of steam in a steaming zone and is thereafterremoved from the steaming zone and transferred to a physically remotewashing zone, the improvement which comprises maintaining the textile ata temperature not below -180 F. during the interval between the steamingoperation and the washing operation.

GEORGE P. VINCENT. ARCHIE LOUIS DUBEAU.

REFERENCES CITED The following references are of record in the file ofthis,patent:

UNITED STATES PATENTS Number OTHER REFERENCES American Dyestuff Reporterfor December 4, 1944, pages 536, 537, 538.

